INSECT IDENTIFICATION KEY

Forensic Science Project

Introduction to Taxonomy

The number of different living organisms on this planet is enormous. This vast diversity of organisms means that biologists must have a system of classification of all these organisms, so that they can be identified and studied. This universal system of names also allows the exchange of information between biologists around the world.

This classification consists of groups within groups, with each group having a different rank. The largest rank is the Kingdom. Most taxonomists use a five kingdom system consisting of Monera, Protista, Fungi, Plantae and Animalia. The smallest rank is the Species. A species is a group of organisms that interbreed in nature. In order, the classification sequence from top to bottom is:

Kingdom
Phylum
Class
Order
Family
Genus
Species

INSECTS

Insects belong to the Kingdom Animalia, the Phylum Arthropoda, Class Insecta. Adult insects have six legs, or three pairs of legs. Their bodies consist of a head, thorax and abdomen.

Carrion insects are those insects found feeding on, or associated with decomposing animal remains. For the purposes of insects found in this type of ecosystem, if it looks like it has more than six legs, it is not an insect, and you will not be able to identify it with these keys.

In order to identify insects found on carrion, you will require a microscope, since many features are too small to be seen properly with the naked eye.

ORDERS

The two most common orders of insects found on carrion are the Diptera and the Coleoptera.

1. Diptera: This order consists of the true flies. Adult flies have only two wings, or one pair of wings. The second pair has evolved into halteres, which are small knobbed structures used for balance and equilibrium. The larvae of flies are called maggots. Maggots do not have legs and appear wormlike. Flies have a complete metamorphosis. Adult flies lay eggs, the eggs hatch into larvae, larvae feed and develop into pupae. The pupa is a non-feeding stage from which the adult fly eventually emerges. Flies may be discovered in any of these stages on carrion, however the adult fly has the most distinguishable features therefore is the easiest of the stages to identify. If you collect eggs, larvae or pupae, rearing it until it reaches the adult stage will allow the easiest identification.
2. Coleoptera: This order consists of the beetles. Adult beetles have four wings, or two pairs, however the front pair have evolved to become hard thickened elytra. These elytra protect the hind pair of wings, which are used for flight. The beetle larvae that you will encounter on carrion have a scleritized head capsule and legs. Similar to flies, beetles have a complete metamorphosis as well. However, it is unlikely that you will collect eggs or pupae. Most likely you will find larvae and adults.

FAMILIES

Now that you have identified what order your insect belongs to, it is time to move to the next level - the family. It is important to remember however, that this is only a key of the major families. If it does not fit one of the descriptions, send your insect in a separate container label unknown for identification.
DIPTERA
There are five major families of diptera found on carrion. These are the:

Key to the Dipteran Families (adult flies only):

1a.	Head, thorax and abdomen without many large bristles, shiny black	Piophilidae
1b.	Head, thorax and abdomen with many short hairs and large bristles, colour variable	2
2a.	Meron with row of bristles	3
2b.	Meron without bristles	4
3a.	A2 curved forward beyond apex of A1, A1 may intersect A2 before wing margin	Fannidae
3b.	A2 not curved forward as above, A1 does not intersect A2 before wing margin	Muscidae
4a.	Abdomen usually metallic blue or green	Calliphoridae
4b.	Abdomen not metallic blue or green, thorax with conspicuous black stripes on gray background	Sarcophagidae

1. Piophilidae are commonly called Cheese skippers, due to the tendency of the maggots to curl and flick. This makes them appear to skip. These flies are usually found in later stages of decay, when the body smells “cheesy”.
2. Fannidae have a distinctive larval and pupal form, making these immature stages readily identifiable.
3. Muscidae are the familiar houseflies found in houses and barns.
4. Calliphoridae, or blowflies are the most abundance maggots on carrion in B.C. The maggots rapidly consume the flesh of carrion. It is these flies that are most often used to determine the elapsed time since death of an homicide victim.
5. Sarcophagidae, or fleshflies are usually large robust flies. These flies have the ability to lay live larvae instead of eggs.

Key to the common Calliphoridae Species (adapted from Hall 1948)

1a.	Remigium with row of hairs	9
1b.	Remigium bare	2
2a.	Lower squama bare, abdomen metallic green	3
2b.	Lower squama haired on top, abdomen metallic blue	5
3a.	Basicosta black	Lucilia illustris (Meigen)
3b.	Basicosta yellow	4
4a.	Three pairs of post sutural acrostichal bristles	Phaenicia sericata (Meigen)
4b.	Two pairs of post sutural acrostichal bristles (Southern Ontario only)	Phaenicia caeruleividiris (Macquart)
5a.	Scutellum with only 2 strong lateral bristles (excluding strong apical pair), lower calyptere nearly always white	6
5b.	Scutellum with 3 or 4 strong lateral bristles (excluding strong apical pair), lower calyptere black with narrow white margin	7
6a.	One or two pairs of post sutural acrostichal bristles, lower calyptere white	Cynomya cadaverina (Robineau-Desvoidy)
6b.	Three pairs of post sutural acrostichal bristles, lower calyptere black	Eucalliphora latifrons (Hough)
7a.	Black face (gena)	8
7b.	Black hairs on orange cheeks (gena)	Calliphora vicina Robineau-Desvoidy
8a.	Black hairs on gena	Calliphora terraenovae Macquart
8b.	Orange hairs on gena	Calliphora vomitoria (Linnaeus)
9a.	Thorax with conspicuous dark strips, southwest Ontario, southern Manitoba	Cochliomyia macellaria (Fabricius)
9b.	Thorax not conspicuously striped	10
10a	Anterior spiracle white or yellow	Phormia regina (Meigin)
10b	Anterior spiracle dark brown or black	Protophormia terraenovae (Robineau-Desvoidy)

COLEOPTERA
There are seven common families of beetles found on decomposing bodies. These include

Key to the families of Coleoptera (Adapted from Borrer et al. 1989)

1a.	Elytra fully covers abdominal segments	2
1b.	Elytra leave at least one abdominal segment visible from above	4
2a.	First abdominal sternum divided by hind coxae, antennae usually filiform	Carabidae
2b.	First abdominal sternum not divided by hind coxae, antennae variable	3
3a.	Usually brightly colored, with pronotum narrower than the base of the elytra	Cleridae
3b.	Not brightly colored, usually oval, or elongate-oval	Dermestidae
4a.	Six or seven abdominal segments visible from above	Staphylinidae
4b.	Fewer than six abdominal segments visible from above	5
5a.	Three or less abdominal segments visible from above	6
5b,	More than three abdominal segments visible from above	Nitidulidae
6a.	Small, broadly oval and black	Histeridae
6b.	Large, often brightly colored	Silphidae

REFERENCES

Anon. 1987 Manual of Nearctic Diptera. Volume 2. Biosystematics Research Centre Ottawa, Ontario. Monograph no 28.
Borrer, D.J., Triplehorn, C.A. and Johnson, N.F. 1989 An Introduction to the study of insects. 6th Edition. Saunders College Publishing, USA. 875 pp.
Hall, D. G. 1948. The Blowflies of North America. Thomas Say Foundation, USA. 477 pp.

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For more information contact: lsandner@cln.etc.bc.ca